I love the idea of arbitration: even the warning article one of the other answers linked to calls out how helpful it is in comparison to the US's court system. I've never personally been involved in a court case, but some friends of mine have, and even in smaller courts, justice takes forever.
However, I could see the need to opt out, if both:
- There was a possibility that StackOverflow could do something to me for which I would need to seek legal recourse. (right now there is not. If SO stops letting me come here to get answers to questions, I simply ask someone else. If SO leaders make fun of me, I simply let it go like water off a duck's back. If worse comes to worst, all I have to do is leave the Internet for a bit and go play outside.)
- The TOS forced a type of arbitration that was lopsided in SO's favor. Now this is the real question I'd like some SO folks to answer: How do we know the arbitration isn't rigged (see that warning article)?
But as long as that is handled, I say cool your jets everyone, opt out if you feel like you need to, but don't go trying to collect other people to opt out with you, and don't act like this is the end of the world (this is just a website, after all, it isn't like us community members are stuck in an employment relationship with SO).